Irrigation machines are known which include a flexible hose with a moving sprinkler apparatus mounted at the end thereof, e.g. a sprinkler boom or a water cannon mounted on a carriage.
The hose is wound onto a horizontal axis drum carried by a chassis suitable for coupling behind a tractor. The drum is rotated by a turbine or by a hydraulic actuator powered by the irrigation water.
French patent application FR-2.442.007 (Rosenqvist) describes an automatic irrigation machine in which the drum is driven by a turbine.
This machine includes a tachometric dynamo which delivers a signal proportional to the speed of rotation of the turbine and which is applied to a regulator that keeps this speed constant.
This regulation does not take account of variations in flow rate and cannot be used to vary the quantity of water during irrigation.
Austrian patent AT-B-384.346 (Bauer) describes an automatic irrigation machine comprising a drum rotated by a turbine which also, by means of a chain transmission, serves to drive a toothed wheel which actuates a switch that transmits pulses to a computer which calculates the speed of displacement of the sprinkler apparatus and which adjusts the speed of rotation of the turbine to keep the speed of displacement of the sprinkler apparatus constant.
The speed regulation described in that document does not take account of variations in the water flow rate and does not make it possible to adjust the amount of water delivered.
Automatic irrigation machines are also known in which the drum is rotated by an actuator, in particular a deformable actuator constituted by a cylindrical bellows made of elastomer, which actuator causes a rocker arm to reciprocate with the free end of the arm carrying a finger or pawl which co-operates with holes or notches or teeth that are regularly spaced apart around the periphery of the drum.
In machines of this prior type, water is admitted into the actuator and is delivered therefrom under the control of a distributor valve or "water rocker" which is mechanically controlled by abutments carried by a rod which is fixed to the rocker arm. This type of control enables a constant speed of rotation to be obtained or else a speed of rotation which varies as a function of the number of turns of hose wound on the drum in order to maintain the linear speed of displacement of the sprinkler apparatus constant.
The object of the present invention is to provide improved machines of this type making it possible to deliver a predetermined quantity of water regardless of variations in the flow rate of the water delivered by the sprinkler apparatus, and making it possible, in particular, to predetermine the quantity of water that is to be delivered and to make it very easy to vary this quantity as a function of weather conditions, of the nature of the terrain or the crop, and even to make it possible to deliver several different quantities of water during a single irrigation cycle.
When the sprinkler apparatus is of the type having a pivoting gun, an object of the present invention is to provide a machine which makes it easy to correct for sprinkling shortfall at the beginning and at the end of an irrigated strip by increasing the quantity of water delivered to these two ends.
A machine in accordance with the invention is of the conventional type including a drum which is rotated by a deformable actuator which causes a rocker arm to reciprocate, the free end of the arm carrying a finger which co-operates with holes that are regularly spaced apart around a ring which is concentric with said drum.